The present disclosure relates generally to automatic hand brakes and more specifically to an automatic release of hand brakes control system.
Hand or parking brakes on rail vehicles generally include a chain connected to the vehicle brakes and wound around a wheel. The brakes are applied by rotating the wheel and tensioning the chain. The hand brake includes a trigger or lever which, when activated, automatically releases the tension on the chain and releases the parking hand brake. To make sure the hand brake is fully released, the release mechanism has a prolonged release mechanical structure.
Two cylinders may be provided on the hand brake to apply the brakes by turning the wheel to tension the chain and a second cylinder to release the brakes by interacting with the release trigger or lever. A pneumatic system to control the two cylinders and the use of parallel manually actuated valves and electro-pneumatic valves are illustrated in U.S. Pat. No. 6,394,559 and U.S. Pat. No. 7,014,275, for example. The apply and release cylinders are activated by the manual valves as long as the manual valves are activated to connect a source of pressure to the cylinder and for a short period there after determined by the choke on the exhaust port of the manual valve.
The actuation of the electro-pneumatic valves as discussed herein may be by an electrically controlled pneumatic (ECP) brake network and through the cars control unit (CCU). The overall control system is described, for example, in U.S. Pat. No. 7,073,753. Remote control of the hand brake by hand-held terminal is described in U.S. Pat. No. 6,175,784.
In a rail vehicle hand brake having a release activated by a pneumatic cylinder, the present control system includes a manual valve having an output connected to a source of pressure at an input when manually activated. A volume is to be charged by the source of pressure. A first choke connects the volume to exhaust. A first pneumatic valve has a pilot port connected to the volume and has an output connected to the source of pressure at an input when the volume is charged to a predetermined pressure to activate the first pneumatic valve and after the manual vale is activated. The output of the first pneumatic valve is connected to the pneumatic cylinder. The volume and the first choke prolong the time the source of pressure is connected to the pneumatic cylinder after the manual valve is activated.
The volume may be connected to the output of the manual valve and charged by the source of pressure when the manual valve is activated. Alternatively, the volume may be selectively connected to either the source of pressure or the pilot port of the first pneumatic valve by a second pneumatic valve. The second pneumatic valve connects the volume to the source of pressure when deactivated and to the pilot port of the first pneumatic valve when activated. A pilot port of the second pneumatic valve is connected to the output of the first pneumatic valve and activated when the first pneumatic valve is activated.
The output of the manual valve is connected to the pilot port of the first pneumatic valve for initially activating the first pneumatic valve. The manual valve may be a rocker valve.
A manifold includes passages for interconnecting and in which is mounted the manual valve, the first pneumatic valve and the first choke. The manifold includes ports for the source of pressure and the pneumatic cylinder. The volume is in the manifold.
Also, the control system may include a manual valve having an output connected to a source of pressure at an input when manually activated and a volume connected to the output of the manual valve and charged by the source of pressure when the manual valve is activated. A choke connects the volume to a source of lower pressure when the volume is charged. The volume and the choke prolong the time the source of pressure is connected to the pneumatic cylinder after the manual valve is activated.
The volume may be connected to the cylinder. Alternatively, the system may include a pneumatic valve having a pilot port connected to the volume and having an output connected to the source of pressure at an input when the volume is charged to a predetermined pressure to activate the pneumatic valve and after the manual valve is activated. The output of the first pneumatic vale is connected to the cylinder.
The system may include an actuator having a piston operatively connected to the manual valve. The volume is in the actuator on a first face of the piston for holding the piston and the manual valve actuated for the prolonged time. The choke continuously connects the volume to a second face of the piston opposite the first face of the piston and may be a passage in the piston. The manual valve is a slide valve having a slide and the piston is the slide of the slide valve. A detent holds the manual valve in the activated position for the prolonged time.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.